1. Field of the Invention
The present invention relates to apparatus for molding plastic bonded magnets and more particularly to apparatus which employs high energy, permanent magnets for magnetizing a ferro-plastic body while it is being molded.
2. Description of the Prior Art
Plastic bonded, permanent magnets are conventional, and in the prior art have been formed of different constituents and have taken many different forms. Typical materials and magnets are disclosed in U.S. Pat. No. 3,872,334 and the references cited therein. In this patent there is disclosed an injection molding apparatus having a molding cavity provided with an electromagnet for magnetizing a molded body while molten. Generally speaking, such apparatus and the magnetizing process are old in the art insofar as the use of electromagnets are concerned, such electromagnets being utilized for the purpose of producing the necessary magnetizing field of a strength sufficient to accomplish the desired magnetization. In the past, permanent magnets have not been used for the reason that the fields developed thereby were not of adequate strength. While permanent magnet materials, such as those from which rare earth magnets are formed, have been known to possess favorable magnetic properties, rare earth magnets have been found to be quite frangible and easily damaged or destroyed when subjected to compressive forces of a magnitude at which plastic parts are injection molded. Other typical prior art is represented by U.S. Pat. No. 4,185,262 wherein ferro-plastic magnets are magnetized subsequent to formation rather than during any molding or forming process.